/Engine/Source/Runtime/Landscape/Classes/LandscapeComponent.h
Update the MaterialInstance parameters to match the layer and weightmaps for this component Creates the MaterialInstance if it doesn't exist.
void UpdateMaterialInstances ( [FMaterialUpdateContext](API\Runtime\Engine\FMaterialUpdateContext) & InOutMaterialContext, [TArray](API\Runtime\Core\Containers\TArray)< class [FComponentRecreateRenderStateContext](API\Runtime\Engine\FComponentRecreateRenderStateCon-) > & InOutRecreateRenderStateContext )